is a trick play.
White is tricked in this diagram.
White cant protect against both a and b. A favourable ladder is desired for black.
is the correct answer, the position is joseki again after
.
example by danoontje
Dave: Yi played in order to end in sente to play
. Note that in this and the other pro games where
has appeared Black always plays tenuki after
. This is a normal, although quite rare, joseki. It may offer opportunities for White to go wrong but what joseki doesn't? :-)